We are combining techniques of quantitative ultrasonic imaging to study polycystic kidney disease (PKD) as the disease progresses to renal failure. Our goal is to use ultrasound noninvasively to detect morphological changes early in the disease process when interventions are most likely to be successful and prior to a significant loss in renal function. We are examining the kidneys of normal rats and those with PKD at various ages with several techniques to obtain comprehensive knowledge of the disease progression. The Han:SPRD rat inherits PKD as an autosomal dominant trait (ADPKD) that closely mimics ADPKD in humans. Changes in renal function are assessed using tracer kinetics (DTPA) and IOH clearance). Ultrasonic techniques, based on measurements of acoustic backscatter coefficients and parameters derived from these measurements, are sensitive to microscopic changes in the tissue morphology. Elasticity imaging is used to study the changes in the tissue macrostructure. All acoustic measurements are made using a state-of-the-art clinical imaging system (Siemens Elegra). Our results show that ultrasonic techniques are very sensitive to early changes in renal microstructure and macrostructure. Ultrasound can be used to detect changes in the renal cortex long before there is a measurable loss of renal function. These techniques are also useful for monitoring the progression of the disease. Most importantly, these techniques are noninvasive and directly applicable to humans.